The present invention relates to a trolling device and particularly to such a device including means for controlling the position of the device in a fluid according to a detected parameter.
A trolling device which can maintain a preselected position as a function of water depth or temperature when attached to a tow line has great utility for oceanographic research where samples of plankton, temperature, salinity, oxygen or other data can be accomplished more quickly and economically through the use of such a device. Present systems employed for such measurements utilize time-consuming procedures wherein tow line angle measurements are made and trigonometric functions are applied to such data to ascertain the position of the sensor in the water.
Alternatively, self-controlled devices such as represented in U.S. Pat. No. 3,412,704 issued Nov. 26, 1968 to P. L. Buller et al. are very complex and expensive including an array of mechanical and electrical parts for sensing the water depth and controlling diving vanes through servo control systems. When utilizing trolling devices for oceanographic research, it is desirable to gather several samples during one trolling run which requires the deployment of several devices from separate lines. The prior art systems require either considerable manpower to utilize or alternatively, several costly devices.
In addition to oceanographic research, constant depth or constant temperature trolling devices of several varieties have been suggested for the sport fisherman for maintaining a fishing lure at a predetermined water temperature or depth at which the desired species of fish is likely to be found. The use of such a device for sport fisherman, or necessity, must be less expensive than that employed in oceanographic research thereby eliminating the relatively complex and, therefore, costly systems. Several fishing devices of this type have been provided which provide for some form of lure control either responsive to depth or water temperature. Representative of known devices are U.S. Pat. Nos. 2,976,642 issued Mar. 28, 1961 to R. J. Wickman et al.; 3,583,089 issued June 8, 1971 to Carl B scarbro; 3,643,370 issued Feb. 22, 1972 to J. W. Cook; and 3,470,649 issued Oct. 7, 1969 to R. O. Cole.
In addition to these devices, U.S. Pat. No. 3,749,045 issued July 31, 1973 to Angus et al. and assigned to the present assignee discloses a pressure-responsive, constant depth trolling device in which a pressure-actuated member is coupled to a diving fin and directly applies force to change the angular position of the diving fin for maintaining the trolling device near a constant depth. In U.S. Pat. No. 3,749,045, the pressure-actuated member pushes the vane against the force of the fluid flowing past. In the present case, the force of the flowing fluid is actually utilized to move the vane to the desired position.
Although such prior art devices have provided some degree of usefulness, particularly in the sport fishing art, they have been limited to pressure- or temperature-responsive applications for controlling the position of the trolling device. An even greater deficiency in such devices is that they require a detector or additional power source which provides significant mechanical force or motion for providing the desired control function. Such limitations, of necessity, reduce the accuracy of the devices in controlling their motion through water, increase the required size and mechanical strength of the detector, increases the mechanical complexity and cost and reduces the number and scope of other applications.